1. Field of the Invention
The present invention relates to the field of computer graphics.
2. Related Art
Offline rendering algorithms have to a great extent conquered physically accurate photo-realism and complex synthetic shading. A result of over twenty years of research, these techniques all solve the lighting or rendering equation in some manner. See, the techniques in Blinn, J. F. and Newell, M. E., Comm. ACM 19:542-546 (1976); Cook, R. L., et al., “The Reyes image rendering architecture,” in Computer Graphics (SIGGRAPH '87 Proc.), vol. 21, Stone, M. C., ed., (July 1987), pp. 95-102; Debevec, P., “Rendering synthetic objects into real scenes: Bridging traditional and image-based graphics with global illumination and high dynamic range photography,” in SIGGRAPH 98 Conf Proc., Cohen, M., ed., Annual Conference Series, ACM SIGGRAPH, Addison Wesley (July 1998), pp. 189-198; He, X. D., et al, “A comprehensive physical model for light reflection,” in Computer Graphics (SIGGRAPH '91 Proc.), vol. 25, Sederberg, T. W., ed. (July 1991), pp. 175-186; Jensen, H. W. and Christensen, P. H., “Efficient simulation of light transport in scenes with participating media using photon maps,” in SIGGRAPH 98 Conf. Proc., Cohen, M., ed., Annual Conference Series, ACM SIGGRAPH, Addison Wesley (July 1998), pp. 311-320; Miller, G. S. and Hoffman, C. R., “Illumination and reflection maps: Simulated objects in simulated and real environments, in SIGGRAPH '84 Advanced Computer Graphics Animation seminar notes (July 1994); Poulin, P. and Fournier, A., “A model for anisotropic reflection,” in Computer Graphics (SIGGRAPH '90 Proc.), vol. 24, Baskett, F., ed., (August 1990), pp. 273-284; Veach, E. and Guibas, L. J., “Metropolis light transport,” in SIGGRAPH 97 Conf Proc., Whitter, T., ed., Annual Conference Series, ACM SIGGRAPH, Addison Wesley (August 1997), pp. 65-76, and the rendering equation in Kajiya, J. T., “The rendering equation,” Computer Graphics (SIGGRAPH '86 Proc.), vol. 20, Evans, D. C. and Athay, R. J., eds., (August 1986), pp. 143-150.
A trade-off between speed and quality exists in off-line rendering and interactive rendering. The outstanding rendering challenge now becomes how to increase the performance of sophisticated shading algorithms without losing the advancements made in quality. This implies that many orders of magnitude in performance improvements must be found. Traditionally, this has been accomplished by vastly simplifying the approximations used in the shading and lighting equations—resulting in a significant loss in complexity and quality.
Environment mapping is one method used to improve the realism of interactive rendering. As originally described by Newell and Blinn (Blinn, J. F. and Newell, M. E., Comm. ACM 19:542-546 (1976)), a simple environment map is used to quickly find reflections of distant objects from a perfectly mirrored surface. Other researchers refined this notion by generalizing the BRDF used, though some of these refinements lost the interactivity of simple environment mapping. See, Cabral, B., et al., “Bidirectional reflection functions from surface bump maps,” in Computer Graphics (SIGGRAPH '87 Proc.), vol. 21, Stone, M. C., ed., (July 1987), pp. 273-281; Greene, N., “Applications of world projections,” in Proc. Graphics Interface '86, Green, M., ed. (May 1986), pp. 108-114; Miller, G. S. and Hoffman, C. R., “Illumination and reflection maps: Simulated objects in simulated and real environments, in SIGGRAPH '84 Advanced Computer Graphics Animation seminar notes (July 1994); Poulin, P. and Fournier, A., “A model for anisotropic reflection,” in Computer Graphics (SIGGRAPH '90 Proc.), vol. 24, Baskett, F., ed., (August 1990), pp. 273-284.
Another method used to bridge the gap between realism and interactivity is image based rendering (McMillan, L. and Bishop, G., “Plenoptic modeling: An image-based rendering system,” in SIGGRAPH 95 Conf Proc., Cook, R., ed., Annual Conference Series, ACM SIGGRAPH, Addison Wesley (August 1995), pp. 39-46). Image based rendering (IBR) avoids solving the lighting equation during interactive rendering by warping existing photographs or images. These images can be thought of as radiance maps (Gershbein, R., et al., “Textures and radiosity: Controlling emission and reflection with texture maps,” in Proc. SIGGRAPH '94 (Orlando, Fla., Jul. 24-29, 1994), Glassner, A., ed., Computer Graphics Proceedings, Annual Conference Series, ACM SIGGRAPH, ACM Press (July 1994), pp. 51-58), and generalized to light fields (Levoy, M. and Hanrahan, P., “Light field rendering,” in SIGGRAPH 96 Conf Proc., Rushmeier, H., ed., Annual Conference Series, ACM SIGGRAPH, ACM Press (August, 1996), pp. 31-42) and lumigraphs (Gortler, S. J., et al, “The lumigraph,” in SIGGRAPH 96 Conf Proc., Rushmeier, H., ed., Annual Conference Series, ACM SIGGRAPH, ACM Press (August, 1996), pp. 43-54). This works well for predefined scenes or images, but not for dynamically changing synthetic objects.
Recently, Debevec (Debevec, P., “Rendering synthetic objects into real scenes: Bridging traditional and image-based graphics with global illumination and high dynamic range photography,” in SIGGRAPH 98 Conf Proc., Cohen, M., ed., Annual Conference Series, ACM SIGGRAPH, Addison Wesley (July 1998), pp. 189-198) combined captured environment maps and synthetic objects to produce compelling renderings with both synthetic objects and image based environments. His techniques do not work at interactive rates since he computes the lighting equation integration as he renders using RADIANCE (Ward, G. J., “The RADIANCE lighting simulation and rendering system,” Proc. SIGGRAPH '94 (Orlando, Fla., Jul. 24-29, 1994), Glassner, A., ed., Computer Graphics Proceedings, Annual Conference Series, ACM SIGGRAPH, ACM Press (July 1994), pp. 459-572).
What is needed is an interactive photo-realistic rendering algorithm or system.